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Practice · Biology · 2025 syllabus · C3.2

IB Biology C3.2 Defence against disease: practice questions

6 exam-style questions on C3.2 Defence against disease, SL and HL: 3 multiple choice, 1 data-based, 1 short answer and 1 extended response. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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C3.2-01 · Paper 1A style · multiple choice · 1 mark

Innate and adaptive immunity

Which row correctly compares the innate and adaptive immune systems? [1]

  1. Innate: responds specifically to particular pathogens; adaptive: responds to broad categories
  2. Innate: does not change during a lifetime; adaptive: builds a memory of pathogens met
  3. Innate: includes B-lymphocytes; adaptive: includes phagocytes
  4. Innate: develops only after vaccination; adaptive: present from birth
Show the answer and the reasoning

Answer: B. B is correct. The innate system responds in the same way to broad categories of pathogen throughout life, whereas the adaptive system responds specifically to each pathogen and keeps memory cells, so later responses are faster and stronger. A reverses the two systems. C also reverses them: phagocytes are innate and B-lymphocytes are adaptive. D reverses them again: the innate system is present from birth, and vaccination works on the adaptive system.

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The 6 questions in C3.2

  1. C3.2-01 Innate and adaptive immunityPaper 1A style · multiple choice · 1 mark
  2. C3.2-02 Response to a second dosePaper 1A style · multiple choice · 1 mark
  3. C3.2-03 How zoonoses reach humansPaper 1A style · multiple choice · 1 mark
  4. C3.2-04 Helper T-cells in HIV infectionPaper 2 style · short answer · 8 marks
  5. C3.2-05 Vaccination and hospital admissionsPaper 1B style · data-based · 9 marks
  6. C3.2-06 Barriers, lymphocytes and resistancePaper 2 style · extended response · 15 marks

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.